Multiple Mobile Robots Map Building Based On AmigoBot Platform

In recent years, the researches on the exploring of the environment and map building with robot have attracted more and more attention with the development of the technology of robots. The study of the map building problem as an important foundation for the autonomous mobile robot navigation has important theoretical significance and practical value. Compared with the single robot task execution, multiple robots can complete the task more efficiently, more adaptablely, more reliably. Therefore, multi-robot system has a broader scope in application and is more suitable for complex, large-scale environment. Domestic and foreign experts and scholars are paying high attention to multi-robot system and make it become the focus of research in this field.In some structured environments, such as office and classroom, straight lines are the main features of the environment. We can identify the obstacles in the environment through the detection of the straight lines. The sonar sensors save the information of the obstacles as the coordinates of the points while collecting the information of the obstacles. So it is necessary to convert the points which are collected by the sonar sensors to the straight lines. Hough Transform is the most common approach but has a large amount of computation. A new line extraction algorithm is proposed in this paper based on incremental method used for the process of map building with the multi-robot to describe the obstacles in the environment with the straight lines to complete the task of exploring.The simulation experiment was made in this paper using the Amigo Bot platform for mobile robots. Amigo Bot mobile robots are equipped with sonar sensors and inertial navigation. Because the data quantity collected by the sonar sensors is big, we select tree instead of array increasing the convenience store and occupying less storage space. Through comparing several common straight line extraction algorithms, this paper proposes incremental line extraction algorithm to achieve line generating and line extension according to several location relationships between points and line segments. Expressing the obstacles in the environment for straight lines, the geometric feature map is chose in this paper finally to describe the map of the environment created by the mobile robots to program in VS2008. The ARIA class used is also introduced in the article. Through the simulation of Mobile Sim, we confirm that the algorithm is feasible and effective.The main contents of this paper are as follows:This paper first respectively introduces four map representations: the raster map, the geometric feature map, the topological map and the mixed map. This paper compares their advantages and disadvantages using geometric feature map which is using straight lines to represent the obstacles to show the explored environment with the robots more vividly and visually.Then this paper introduces the sensors. Because the Amigo Bot robots are equipped with sonar sensors and inertial navigations, this paper expounds the principles and the characteristics of the sonar sensor and inertial navigations to pave the way for the algorithm.Then the paper describes the data storage structure. The arrays and linked lists are two kinds of the common storage modes. Each of the Amigo Bot robots is equipped with eight sonar sensors. Because the sonar sensors will collect information of the obstacles per cycle, the amount of data acquisition of the sonar sensors is larger. If you use an array of storage, a large amount of memory will be occupied. So we choose the tree structure to store data to add, delete and replace the data conveniently.Then this paper compares the advantages and disadvantages of three kinds of line extraction algorithms of Hough Transform, the incremental method and the RANSAC method. This paper presents an incremental line extraction algorithm according to some location relationships of points and line segments. This algorithm will convert the data points of the obstacles collected by the sonar sensors to line to represent obstacles ultimately to get the explored environment map with the robots.This paper introduces Amigo Bot robot software platform to program in VS2008. Several classes of ARIA used in the programming process are also listed relating to the motion control and the location information of the robots, the information acquisition of the sonar sensors. And then the Mobile Sim simulation experiments are performed to verify the validity of the algorithm.